Skip to content
Omnikalc

Tympanometry static admittance and ear canal volume calculator

Enter the admittance at the peak, the admittance at +200 daPa and the pressure of the peak to get the static admittance, the equivalent ear canal volume and the tympanogram type, with the flags for a perforation or a stiff or flaccid middle ear.

Updated on
Your inputs
mL

Value out of range

mL

Value out of range

daPa

Value out of range

Results

Static admittance (peak − ear canal volume)

0.60 mL

Type A: a normal tympanogram
Equivalent ear canal volume
0.40 mL
Within the usual range of an ear canal

The tympanometry calculator gives the static admittance, the ear canal volume and the tympanogram type from the admittance at the peak, the admittance at +200 daPa and the pressure of the peak.

How the calculation works

  • Enter the admittance at the peak and at +200 daPa.
  • Enter the pressure of the peak.
  • Read the static admittance, the volume and the type.

Example

An admittance of 1.00 mL at the peak and 0.40 mL at +200 daPa gives a static admittance of 1.00 − 0.40 = 0.60 mL and an ear canal volume of 0.40 mL. With a peak at −20 daPa, the tympanogram is a normal type A. A flat curve with 0.4 mL at both points would give a static admittance near 0 and would be a type B.

Why it matters

The calculator helps audiology and ENT students, school nurses, general practitioners and parents who want to understand a report of a middle ear screening, for example after repeated ear infections.

Good to know

The 226 Hz probe tone is the standard for adults and children, but for babies under about six months the middle ear behaves differently, with a dominant mass, and a higher probe frequency such as 1000 Hz is recommended. Ranges of normal values depend on age and on the instrument, and the ones given here are typical values for adults, with children having lower static admittance and smaller canal volumes. A flat curve can have different causes that are told apart by the canal volume: a small volume points to wax or a probe blocked against the wall, a normal volume to fluid, and a large volume to a hole in the eardrum or an open ventilation tube. Tympanometry tests the mechanics of the middle ear and not the hearing, so it is combined with audiometry and with the acoustic reflexes. A result outside the norm should be assessed by a clinician, who will consider the history and the examination of the ear.

The air-bone gap calculator separates conductive from sensorineural loss, the ear canal calculator treats the resonance of the canal, the pure-tone average calculator grades hearing loss and the DPOAE calculator treats the screening of the cochlea.

Frequently asked questions

What is a tympanogram?

It is a graph of the admittance of the ear, measured with a 226 Hz probe tone, as the air pressure in the sealed canal is varied from positive to negative. The eardrum moves most freely at the pressure that matches the pressure in the middle ear, which gives a peak.

How is static admittance computed?

The admittance at +200 daPa is that of the canal air alone, because the eardrum is stiffened by the pressure. Subtracting it from the admittance at the peak removes the canal and leaves the contribution of the middle ear.

What are the Jerger types?

Type A is a normal peak near zero pressure, A-shallow (As) and A-deep (Ad) have a low or high peak, type B is a flat curve and type C has a peak at a negative pressure. They suggest a cause but do not give a diagnosis.

Was this calculator helpful?

Thanks for your feedback!

Results are estimates provided for information purposes. They do not replace professional advice.

Related calculators